The present invention relates in general to an electronic system for controlling or regulating the main operational parameters of an internal combustion engine, preferably non-load rotary speed or the amount of fuel to be metered, on dependency of auxiliary parameters such as rotary speed, weight rate of airflow in suction pipe, position of throttle valve, pressure in suction pipe, atmospheric pressure or temperature.
Regulating systems of this kind are designed to meet a variety of requirements such as, for example, driving behavior of a motor vehicle equipped with the internal combustion engine, composition of exhaust gas, and a minimum fuel consumption. In regulating stoichiometric values of sucked-in fuel mixture and of values close to the latter in an internal combusion engine having an externally applied ignition, it is necessary to determine the weight rate of air flow in the suction pipe. For this purpose there are known measuring systems using flip valve meters for the amount of air or air mass meters using heating wire. According to the measured weight rate of air flow a corresponding raising signal for fuel is generated.
In order to achieve in the case of a no-load operation the smallest possible consumption of fuel, no-load rotary speed regulators have been applied which take care of maintaining a minimum no-load rotary speed which remains constant even when sudden load changes occur. An example of the no-load rotary speed regulator of this type is described in German publication No. 3,039,435. Due to the fact that rotary speed fluctuations in the last instance are reactions of I.C engine to outer influences and hence the rotary speed signals represent the last stage in the regulating chain, it takes of necessity a certain time period from the start of an action on the I.C. engine to the occurrence of a reaction. In an I.C. engine running at extremely low rotations during no-load conditions the danger is present that the cycles turn around regularly in the case when the regulating system operates at a low rotary speed limit.
In order to avoid this uncertainity factor other known no-load regulating systems attempt to determine parameters which react faster to external influences and evaluate these parameters for regulating purposes.
Publication WO-Al No. 81/01 591 teaches how to apply suction pressure of an I.C. engine for its no-load speed regulation. This known device, however, utilizes the suction pressure only and therefore it cannot guarantee an exact adherence to the no-load or idling rotary speed.